1. INTRODUCTION AND RATIONALE Since sedation is increasingly administered by non-anesthesiologists, patient safety during sedation became of increased interest by the Joint Commission for Accreditation of Healthcare Organisations (JCAHO). The current standard of respiratory monitoring for patients during sedation is continuous pulse oximetry with visual assessment of the patient. Clinical research has demonstrated that hypoxemia, secondary to depressed respiratory activity, is a principal risk during sedation. Microstream capnography is a relatively new technology for carbon dioxide (CO2) monitoring. The technique is based on emission of selective infrared wavelengths exactly matching for CO2 absorption. Due to this efficient and selective emission process only small samples of CO2 are necessary to detect alveolar hypoventilation, and accuracy is maintained with a low flow sample rate. Therefore, capnography can provide more useful information on the frequency, effectiveness and regularity of ventilation, than pulse oximetry during procedures accomplished under deep sedation. According to previous reports capnography provides early detection of alveolar hypoventilation before hypoxemia has occurred in nonintubated patients and thereby can improve patient safety during sedation.